Media stackers typically include wheels that are used to collate media items, such as banknotes, to enable those collated media items to be conveyed as a bunch.
A stacker wheel typically comprises an axially-mounted hub, and a plurality of arcuate tines extending transverse to the axle on which the hub is mounted.
A stacker unit comprises a plurality of mutually coupled but axially separated stacker wheels. The stacker wheels are rotated in unison as media items are fed into the stacker wheels from one side (the media item input side). The speed at which the media items are conveyed is synchronized with the rotation of the stacker wheels so that only one media item is stored between adjacent tines.
A pivoting collecting plate is typically located at the opposite side of the stacker unit to the media item input side. The collecting plate comprises a plurality of arms, each arm extending between adjacent stacker wheels. As the stacker wheels rotate, media items stored in the stacker unit engage with the arms, which remove the media items from the stacker unit and arrange them as a bunch of media items. The collecting plate is then pivoted away from the stacker unit and the bunch of media items can be transported.
One problem associated with a stacker unit is that it is possible for a media item to collide with the end of a tine of a stacker wheel, so that the media item crumples and jams the stacker unit instead of entering the stacker unit.
U.S. Pat. No. 6,554,273 attempts to solve this problem by monitoring the trailing edge of a note as it enters the stacker wheel and adjusting the rotational speed of the stacker wheels accordingly. This requires accurate measurement of the media item being transported and accurate control of the stacker wheel speed.
It is among the objects of an embodiment of the present invention to mitigate the above problem or another problem associated with prior art stacker wheels or stacker units.